﻿// Copyright (c) 2011 AlphaSierraPapa for the SharpDevelop Team
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

using System;
using System.Collections.Generic;
using System.Linq;
using Mono.Cecil;
using Mono.Cecil.Cil;

namespace RoslynPad.Hosting.ILDecompiler
{
    /// <summary>
    /// Cecil helper methods.
    /// </summary>
    internal static class CecilExtensions
    {
        #region GetPushDelta / GetPopDelta
        public static int GetPushDelta(this Instruction instruction)
        {
            var code = instruction.OpCode;
            switch (code.StackBehaviourPush)
            {
                case StackBehaviour.Push0:
                    return 0;

                case StackBehaviour.Push1:
                case StackBehaviour.Pushi:
                case StackBehaviour.Pushi8:
                case StackBehaviour.Pushr4:
                case StackBehaviour.Pushr8:
                case StackBehaviour.Pushref:
                    return 1;

                case StackBehaviour.Push1_push1:
                    return 2;

                case StackBehaviour.Varpush:
                    if (code.FlowControl != FlowControl.Call)
                        break;

                    var method = (IMethodSignature)instruction.Operand;
                    return IsVoid(method.ReturnType) ? 0 : 1;
            }

            throw new NotSupportedException();
        }

        public static int? GetPopDelta(this Instruction instruction, MethodDefinition methodDef)
        {
            var code = instruction.OpCode;
            switch (code.StackBehaviourPop)
            {
                case StackBehaviour.Pop0:
                    return 0;
                case StackBehaviour.Popi:
                case StackBehaviour.Popref:
                case StackBehaviour.Pop1:
                    return 1;

                case StackBehaviour.Pop1_pop1:
                case StackBehaviour.Popi_pop1:
                case StackBehaviour.Popi_popi:
                case StackBehaviour.Popi_popi8:
                case StackBehaviour.Popi_popr4:
                case StackBehaviour.Popi_popr8:
                case StackBehaviour.Popref_pop1:
                case StackBehaviour.Popref_popi:
                    return 2;

                case StackBehaviour.Popi_popi_popi:
                case StackBehaviour.Popref_popi_popi:
                case StackBehaviour.Popref_popi_popi8:
                case StackBehaviour.Popref_popi_popr4:
                case StackBehaviour.Popref_popi_popr8:
                case StackBehaviour.Popref_popi_popref:
                    return 3;

                case StackBehaviour.PopAll:
                    return null;

                case StackBehaviour.Varpop:
                    if (code == OpCodes.Ret)
                        return methodDef.ReturnType.IsVoid() ? 0 : 1;

                    if (code.FlowControl != FlowControl.Call)
                        break;

                    var method = (IMethodSignature)instruction.Operand;
                    var count = method.HasParameters ? method.Parameters.Count : 0;
                    if (method.HasThis && code != OpCodes.Newobj)
                        ++count;
                    if (code == OpCodes.Calli)
                        ++count; // calli takes a function pointer in additional to the normal args

                    return count;
            }

            throw new NotSupportedException();
        }

        public static bool IsVoid(this TypeReference type)
        {
            while (type is OptionalModifierType || type is RequiredModifierType)
                type = ((TypeSpecification)type).ElementType;
            return type.MetadataType == MetadataType.Void;
        }

        public static bool IsValueTypeOrVoid(this TypeReference type)
        {
            while (type is OptionalModifierType || type is RequiredModifierType)
                type = ((TypeSpecification)type).ElementType;
            if (type is ArrayType)
                return false;
            return type.IsValueType || type.IsVoid();
        }

        /// <summary>
        /// checks if the given TypeReference is one of the following types:
        /// [sbyte, short, int, long, IntPtr]
        /// </summary>
        public static bool IsSignedIntegralType(this TypeReference type)
        {
            return type.MetadataType == MetadataType.SByte ||
                   type.MetadataType == MetadataType.Int16 ||
                   type.MetadataType == MetadataType.Int32 ||
                   type.MetadataType == MetadataType.Int64 ||
                   type.MetadataType == MetadataType.IntPtr;
        }

        /// <summary>
        /// checks if the given value is a numeric zero-value.
        /// NOTE that this only works for types: [sbyte, short, int, long, IntPtr, byte, ushort, uint, ulong, float, double and decimal]
        /// </summary>
        public static bool IsZero(this object value)
        {
            return value.Equals((sbyte)0) ||
                   value.Equals((short)0) ||
                   value.Equals(0) ||
                   value.Equals(0L) ||
                   value.Equals(IntPtr.Zero) ||
                   value.Equals((byte)0) ||
                   value.Equals((ushort)0) ||
                   value.Equals(0u) ||
                   value.Equals(0UL) ||
                   value.Equals(0.0f) ||
                   value.Equals(0.0) ||
                   value.Equals((decimal)0);

        }

        #endregion

        /// <summary>
        /// Gets the (exclusive) end offset of this instruction.
        /// </summary>
        public static int GetEndOffset(this Instruction inst)
        {
            if (inst == null)
                throw new ArgumentNullException(nameof(inst));
            return inst.Offset + inst.GetSize();
        }

        public static string OffsetToString(int offset)
        {
            return $"IL_{offset:x4}";
        }

        public static HashSet<MethodDefinition> GetAccessorMethods(this TypeDefinition type)
        {
            var accessorMethods = new HashSet<MethodDefinition>();
            foreach (var property in type.Properties)
            {
                accessorMethods.Add(property.GetMethod);
                accessorMethods.Add(property.SetMethod);
                if (property.HasOtherMethods)
                {
                    foreach (var m in property.OtherMethods)
                        accessorMethods.Add(m);
                }
            }
            foreach (var ev in type.Events)
            {
                accessorMethods.Add(ev.AddMethod);
                accessorMethods.Add(ev.RemoveMethod);
                accessorMethods.Add(ev.InvokeMethod);
                if (ev.HasOtherMethods)
                {
                    foreach (var m in ev.OtherMethods)
                        accessorMethods.Add(m);
                }
            }
            return accessorMethods;
        }

        public static TypeDefinition ResolveWithinSameModule(this TypeReference type)
        {
            if (type != null && type.GetElementType().Module == type.Module)
                return type.Resolve();
            return null;
        }

        public static FieldDefinition ResolveWithinSameModule(this FieldReference field)
        {
            if (field != null && field.DeclaringType.GetElementType().Module == field.Module)
                return field.Resolve();
            return null;
        }

        public static MethodDefinition ResolveWithinSameModule(this MethodReference method)
        {
            if (method != null && method.DeclaringType.GetElementType().Module == method.Module)
                return method.Resolve();
            return null;
        }

        [Obsolete("throwing exceptions is considered a bug")]
        public static TypeDefinition ResolveOrThrow(this TypeReference typeReference)
        {
            var resolved = typeReference.Resolve();
            if (resolved == null)
                throw new Exception("ReferenceResolving");
            return resolved;
        }

        public static bool IsCompilerGenerated(this ICustomAttributeProvider provider)
        {
            if (provider != null && provider.HasCustomAttributes)
            {
                foreach (var a in provider.CustomAttributes)
                {
                    if (a.AttributeType.FullName == "System.Runtime.CompilerServices.CompilerGeneratedAttribute")
                        return true;
                }
            }
            return false;
        }

        public static bool IsCompilerGeneratedOrIsInCompilerGeneratedClass(this IMemberDefinition member)
        {
            if (member == null)
                return false;
            if (member.IsCompilerGenerated())
                return true;
            return IsCompilerGeneratedOrIsInCompilerGeneratedClass(member.DeclaringType);
        }

        public static TypeReference GetEnumUnderlyingType(this TypeDefinition type)
        {
            if (!type.IsEnum)
                throw new ArgumentException("Type must be an enum", nameof(type));

            var fields = type.Fields;

            foreach (var field in fields)
            {
                if (!field.IsStatic)
                    return field.FieldType;
            }

            throw new NotSupportedException();
        }

        public static bool IsAnonymousType(this TypeReference type)
        {
            if (type == null)
                return false;
            if (string.IsNullOrEmpty(type.Namespace) && type.HasGeneratedName() && (type.Name.Contains("AnonType") || type.Name.Contains("AnonymousType")))
            {
                var td = type.Resolve();
                return td != null && td.IsCompilerGenerated();
            }
            return false;
        }

        public static bool HasGeneratedName(this MemberReference member)
        {
            return member.Name.StartsWith("<", StringComparison.Ordinal);
        }

        public static bool ContainsAnonymousType(this TypeReference type)
        {
            if (type is GenericInstanceType git)
            {
                return IsAnonymousType(git) || git.GenericArguments.Any(t => t.ContainsAnonymousType());
            }

            var typeSpec = type as TypeSpecification;
            return typeSpec != null && typeSpec.ElementType.ContainsAnonymousType();
        }

        public static string GetDefaultMemberName(this TypeDefinition type)
        {
            return type.GetDefaultMemberName(out var _);
        }

        public static string GetDefaultMemberName(this TypeDefinition type, out CustomAttribute defaultMemberAttribute)
        {
            if (type.HasCustomAttributes)
                foreach (var ca in type.CustomAttributes)
                    if (ca.Constructor.DeclaringType.Name == "DefaultMemberAttribute" && ca.Constructor.DeclaringType.Namespace == "System.Reflection"
                        && ca.Constructor.FullName == @"System.Void System.Reflection.DefaultMemberAttribute::.ctor(System.String)")
                    {
                        defaultMemberAttribute = ca;
                        return ca.ConstructorArguments[0].Value as string;
                    }
            defaultMemberAttribute = null;
            return null;
        }

        public static bool IsIndexer(this PropertyDefinition property)
        {
            return property.IsIndexer(out var _);
        }

        public static bool IsIndexer(this PropertyDefinition property, out CustomAttribute defaultMemberAttribute)
        {
            defaultMemberAttribute = null;
            if (property.HasParameters)
            {
                var accessor = property.GetMethod ?? property.SetMethod;
                var basePropDef = property;
                if (accessor.HasOverrides)
                {
                    // if the property is explicitly implementing an interface, look up the property in the interface:
                    var baseAccessor = accessor.Overrides.First().Resolve();
                    if (baseAccessor != null)
                    {
                        foreach (var baseProp in baseAccessor.DeclaringType.Properties)
                        {
                            if (baseProp.GetMethod == baseAccessor || baseProp.SetMethod == baseAccessor)
                            {
                                basePropDef = baseProp;
                                break;
                            }
                        }
                    }
                    else
                        return false;
                }
                var defaultMemberName = basePropDef.DeclaringType.GetDefaultMemberName(out CustomAttribute attr);
                if (defaultMemberName == basePropDef.Name)
                {
                    defaultMemberAttribute = attr;
                    return true;
                }
            }
            return false;
        }

        public static bool IsDelegate(this TypeDefinition type)
        {
            if (type.BaseType != null && type.BaseType.Namespace == "System")
            {
                if (type.BaseType.Name == "MulticastDelegate")
                    return true;
                if (type.BaseType.Name == "Delegate" && type.Name != "MulticastDelegate")
                    return true;
            }
            return false;
        }
    }
}
